Recent advancements in natural dye applications: a review

During the resorbable-polymer-boom of the 1970s and 1980s, polycaprolactone (PCL) was used in the biomaterials field and a number of drug-delivery devices. Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption pathways; consequently, PCL was almost forgotten for most of two decades. Recently, a resurgence of interest has propelled PCL back into the biomaterials-arena. The superior rheological and viscoelastic properties over many of its aliphatic polyester counterparts renders PCL easy to manufacture and manipulate into a large range of implants and devices. Coupled with relatively inexpensive production routes and FDA approval, this provides a promising platform for the production of longer-term degradable implants which may be manipulated physically, chemically and biologically to possess tailorable degradation kinetics to suit a specific anatomical site. This review will discuss the application of PCL as a biomaterial over the last two decades focusing on the advantages which have propagated its return into the spotlight with a particular focus on medical devices, drug delivery and tissue engineering.

The return of a forgotten polymer : Polycaprolactone in the 21st century

Surface modification and endothelialization of vascular biomaterials are common approaches that are used to both resist the nonspecific adhesion of proteins and improve the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification of vascular grafts using hydrophilic poly(ethylene glycol), zwitterionic polymers, heparin or other bioactive molecules can efficiently enhance hemocompatibility, and consequently prevent thrombosis on artificial vascular grafts. However, these modified surfaces may be excessively hydrophilic, which limits initial vascular endothelial cell adhesion and formation of a confluent endothelial lining. Therefore, the improvement of endothelialization on these grafts by chemical modification with specific peptides and genes is now arousing more and more interest. Several active peptides, such as RGD, CAG, REDV and YIGSR, can be specifically recognized by endothelial cells. Consequently, graft surfaces that are modified by these peptides can exhibit targeting selectivity for the adhesion of endothelial cells, and genes can be delivered by targeting carriers to specific tissues to enhance the promotion and regeneration of blood vessels. These methods could effectively accelerate selective endothelial cell recruitment and functional endothelialization. In this review, recent developments in the surface modification and endothelialization of biomaterials in vascular tissue engineering are summarized. Both gene engineering and targeting ligand immobilization are promising methods to improve the clinical outcome of artificial vascular grafts.

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Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

[Low-molecular-weight heparins].

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. To fit functional demand, materials with desired physical, chemical, biological, biomechanical, and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Biomedical applications of biodegradable polymers

Sutures are a vital part for surgical operation, and suture-associated surgical site infections are an important issue of postoperative care. Antibacterial sutures have been proved to reduce challenging complications caused by bacterial infections. In recent decades, triclosan-free sutures have been on their way to commercialization. Alternative antibacterial substances are becoming relevant to processing surgical suture materials. Most of the antibacterial substances are loaded directly on sutures by dipping or coating methods. The aim of this study was to optimize novel antibacterial braided silk sutures based on levofloxacin hydrochloride and poly(e-caprolactone) by two different processing sequences, to achieve suture materials with slow-release antibacterial efficacy and ideal physical and handling properties. Silk strands were processed into sutures on a circular braiding machine, and antibacterial treatment was introduced alternatively before or after braiding by two-dipping-two-rolling method (M1 group and M2 group). The antibacterial activity and durability against Staphylococcus aureus and Escherichia coli were tested. Drug release profiles were measured in phosphate buffer with different pH values, and release kinetics model was built to analyze the sustained drug release mechanism between the interface of biomaterials and the in vitro aqueous environment. Knot-pull tensile strength, thread-to-thread friction, and bending stiffness were determined to evaluate physical and handling properties of sutures. All coated sutures showed continuous antibacterial efficacy and slow drug release features for more than 5 days. Besides, treated sutures fulfilled U.S. Pharmacopoeia required knot-pull tensile strength. The thread-to-thread friction and bending stiffness for the M1 group changed slightly when compared with those of uncoated ones. However, physical and handling characteristics of the M2 group tend to approach those of monofilament ones. The novel suture showed acceptable in vitro cytotoxicity according to ISO 10993-5. Generally speaking, all coated sutures show potential in acting as antibacterial suture materials, and M1 group is proved to have a higher prospect for clinical applications.

Antibacterial Surgical Silk Sutures Using a High-Performance Slow-Release Carrier Coating System.

Novel antibacterial nanomaterials have been developed for biomedical applications. The present study involves the preparation and properties of antibacterial nanofibers from chitosan/polyethylene o...

Antibacterial wound dressing from chitosan/polyethylene oxide nanofibers mats embedded with silver nanoparticles.

The aim of this study was to develop novel biomedical electrospun nanofiber mats for controlled drug release, in particular to release a drug directly to an injury site to accelerate wound healing. Here, nanofibers of chitosan (CS), poly(ethylene oxide) (PEO), and a 90 : 10 composite blend, loaded with a fluoroquinolone antibiotic, such as ciprofloxacin hydrochloride (CipHCl) or moxifloxacin hydrochloride (Moxi), were successfully prepared by an electrospinning technique. The morphology of the electrospun nanofibers was investigated by scanning electron microscopy. The functional groups of the electrospun nanofibers before and after crosslinking were characterized by Fourier transform infrared spectroscopy. X-ray diffraction results indicated an amorphous distribution of the drug inside the nanofiber blend. In vitro drug-release evaluations showed that the crosslinking could control the rate and period of drug release in wound-healing applications. The inhibition of bacterial growth for both Escherichia coli and Staphylococcus aureus were achieved on the CipHCl- and Moxi-loaded nanofibers. In addition, both types of CS/PEO and drug-containing CS/PEO nanofibers showed excellent cytocompatibility in the cytotoxicity assays. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42060.

Composite chitosan/poly(ethylene oxide) electrospun nanofibrous mats as novel wound dressing matrixes for the controlled release of drugs

Surgical braided silk sutures have been widely used because these materials exhibit good handling characteristics, ease of use, and ideal knot security. However, surgical silk sutures likely cause surgical site infections because these sutures are composed of natural protein materials with a braided structure. As such, antibacterial silk sutures for clinical wound closure should be developed. Braided silk suture could be treated and modified with antibacterial agent, provided that excellent physical and handling characteristics of this material should maximize maintained. This study aimed to quantitatively investigate the effect of antibacterial treatment with different parameters on physical and handling characteristics of novel antibacterial braided silk sutures. Physical and handling characteristics, including appearance, knot-pull tensile strength, pullout friction resistance, tissue drag friction resistance, and bending stiffness, were evaluated. After physical and handling tests were conducted, images showed morphological characteristics were obtained and evaluated to investigate the relationship between antibacterial treatment and physical and handling properties. Results showed that suture diameter increased and reached the nearest thick size specification; knot-pull tensile strength decreased but remained higher than the standard value by at least 40.73%. Fracture asynchronism during knot-pull tensile strength test suggested that the fineness ratio of shell and core strands may enhance knot-pull tensile strength. Static and dynamic frictions of suture-to-suture friction behavior were slightly affected by antibacterial treatment, and changed to less than 16.07% and 32.77%, respectively. Suture-to-tissue friction and bending stiffness increased by approximately 50%; the bending stiffness of the proposed suture remained efficient compared with that of synthetic sutures. Therefore, good physical and handling characteristics can be maintained by selecting appropriate coating parameters.

Quantitative physical and handling characteristics of novel antibacterial braided silk suture materials

This paper discusses the ultraviolet protective properties of silk fabrics using vegetable dyes extracted from Flos Sophorae. It was found that the aqueous solution of this vegetable dye has excellent thermal stability as well as stability in acid conditions. With the objective of achieving the greatest absorbency in the ultraviolet region, the following optimum extraction conditions were obtained for Flos Sophorae: extraction temperature of 100°C, extraction time of 60 min, and material to liquor ratio of 1:10. The UPF and T(UVA)AV values for the silk fabric dyed by the optimum dye solution were found to meet the Chinese National Standard (UPF = 69 > 30, T(UVA)AV = 1.07% < 5%). According to the standard, the silk fabric can claim to be a “UV-Protective product”. The relation between the UPF value and the K/S value was also studied.

Lu Wang

Papers

Antibacterial Surgical Silk Sutures Using a High-Performance Slow-Release Carrier Coating System.

Antibacterial wound dressing from chitosan/polyethylene oxide nanofibers mats embedded with silver nanoparticles.

Composite chitosan/poly(ethylene oxide) electrospun nanofibrous mats as novel wound dressing matrixes for the controlled release of drugs

Quantitative physical and handling characteristics of novel antibacterial braided silk suture materials

Research on Dyeing and Ultraviolet Protection of Silk Fabric Using Vegetable Dyes Extracted from Flos Sophorae